New Approach Invites Wake Turbulence Encounters

Air Safety Week, Dec 20, 2004

However, the FAA's Great Lakes Region office decided before this memorandum was issued to place the LDA at runway 24R. That decision was based in part on an environmental impact statement (EIS), which is to say an airport noise analysis.

According to sources, the concrete slab for the LDA at runway 24L has been poured, but it is not too late to reposition the LDA to runway 24R. The costs of any such change will increase significantly once power cables, antennae and such are put in place.

Since August, ALPA has urged FAA headquarters to reconsider placement of the LDA at runway 24L and reliance upon the containment box stratagem to minimize wake turbulence encounters. Two ALPA letters on the matter have gone unanswered by the FAA.

The ALPA concerns might be summed up thusly:

* The airport noise analysis of some years ago may not reflect the greater number of regional jet aircraft operations at Cleveland. They are quieter, and the noise "footprint" of the mix of aircraft employed for the original SOIA analysis (and underlying the rationale for placing the LDA at runway 24L) may no longer be applicable.

* Pilots traditionally have been trained to stay above and behind an aircraft on descent ahead, and now they're being required to stay below, behind and inside a moving box.

* The proposed SOIA procedure for Cleveland has national implications, as it changes how pilots separate themselves to avoid wake turbulence. ALPA regards the SOIA proposal for Cleveland as a "bad precedent" that could evolve into an accepted standard.

* A training cost is involved to familiarize pilots with the proposed SOIA at Cleveland, or other procedures with similar geometry. (ASW note: there is an unclear impact on simulator time, given already important evolutions regarding line oriented flight training, LOFT, and recurrent training; it seems likely that more simulators will have to be pressed into service for SOIA participating airlines.)

* Controllers and pilots each have only half the information necessary. The pilot knows the wind at altitude (through the airplane's flight management system) but not the precise distance to the airplane ahead. The controller knows the distance separating the two aircraft (via radar), but not the wind at altitude.

* Regional jets (RJs) are considered large aircraft for separation purposes (i.e., at least three miles in trail of another large aircraft). Thus, an EMB 135 weighing 32,000 pounds can be placed just three miles behind an A321 landing at 160,000 pounds (large aircraft are those with maximum takeoff weights ranging from 41,000 lbs. to 255,000 lbs. - obviously, they'll weigh less on landing). ALPA believes that the "large" weight classification for RJs needs to be evaluated (were RJs to be reclassified to "small" aircraft, a four-mile separation to large aircraft would be required, another factor involving arrival rates and airport productivity).

* The National Air Traffic Controllers Association (NATCA) is opposed to sorting aircraft by weight - which at Cleveland might conceivably involve placing RJs on the 24R approach and heavier aircraft on the 24L approach.